The angle that a blade addresses or is disposed to a sharpening surface determines the sharpness of the blade as well as determining how long the edge will last before dulling. All knives have an optimum blade setting which will, when sharpened at that angle, give a sharp cutting edge that will last for an extended period of time before needing re-sharpening.
The above is particularly important in knives that are used professionally, such as in meat packing house, poultry packing houses, seafood processing plants, and the like where razor sharp knives are needed to keep worker production up and to prevent excessive worker fatigue.
Even experienced meat cutters have difficulty in consistently setting the correct angle of the blade against the sharpener to obtain maximum sharpness while at the same time putting an edge on the knife that will not dull quickly. If the angle is less than optimum, the edge will be so thin that it will quickly dull while if the angle is greater than optimum, then the cutting edge will be blunt and will not take a sharp edge.
At each worker station in meat processing plants there is usually provided a sharpening rod to allow the worker to resharpen his or her knife as needed. There also is usually a smooth steel rod so that a few strokes on the same will allow the worker to maintain a superbly sharp edge. Neither of these rods will give satisfactory results, however, if the angle that the knife blade is held to the rod is incorrect.
Various blade holders and guides have been developed to set the correct angle of knives, scissors and tool blades to sharpening means, whether it be a sharpening rod, flat stone, grinding wheel, or the like. Each of these blade holders, however, are either difficult and complicated to use, or are of a set angle which makes them not readily adaptable to different types and sizes of knives which require different angle of address to the sharpening means to achieve the optimum edge on the knife blade.